Thread: using malloc method to hold the converted data to string/char array

I would like to convert my code that uses an array that's constantly allocated to hold the converted data from an analog to digital converter into a method where the result of the sprintf conversion would be stored in a pointer as long as I need it. Below shows two versions of my code and the red highlighted line shows the task that I'm having trouble with. I apologize for the lackluster tab formatting of the code in advance. Thanks.

explicitly allocated char array version:

Code:

// Data Logging Scale                 <[email protected]>
// Created: Nov 3, 2007
// Revised: Nov 15, 2007

#include <built_in.h>
#include "typedefs.h"
#include "usart.h"
#include "LCD4.h"

#define BUFFER_SIZE 5

void delay(uint number)
{
      while(--number > 0);
}

void main() {
  uint temp_res, last_temp_res;
  int n;
  char adc[BUFFER_SIZE];            // temporary adc string value

  OSCCON = 0x70;        /* internal oscillator at 8 Mhz, system clock = internal oscillator*/
  OSCTUNE = 0x00;        /* oscillator tuning register at max frequency */
 	CMCON = 7;              // turn off comparators
 	Delay_ms(20);            // system wide delay of 20 ms
 	
  ADCON1 = 0x0e;          // Configure Vref and AN0
  TRISA  = 0x01;          // PORTA is output except RA0 (AN0)
  TRISB  = 0x00;          // all PORTB pins are output
  TRISC  = 0x00;          // PORTC is outputs
  
  LCD4_INIT();            // initialize the LCD
  LCD4_OUT("Weight (kg) : ");       // output some text
  

  while(1)
  {
    temp_res = Adc_Read(0);
    n = sprintf(adc, "%u", temp_res);
    if (n < 0 || n >= BUFFER_SIZE)
      break;
    if (abs(temp_res - last_temp_res) < 10)
    {
          LCD4_CMD(142);                   // move cursor position to character #15
          LCD4_OUT(adc);              // output the a/d result
    }
    last_temp_res = temp_res;
  }
}

malloc for a char pointer version:

Code:

// Data Logging Scale                 <[email protected]>
// Created: Nov 3, 2007
// Revised: Dec 15, 2007

#include <built_in.h>
#include "typedefs.h"
#include "usart.h"
#include "LCD4.h"

#define BUFFER_SIZE 5

void delay(uint number)
{
      while(--number > 0);
}

void main() {
  uint temp_res, last_temp_res;
  char *temp_res_text;               // dynamic character array pointer
  int n;

  OSCCON = 0x70;        /* internal oscillator at 8 Mhz, system clock = internal oscillator*/
 	OSCTUNE = 0x00;        /* oscillator tuning register at max frequency */
 	CMCON = 7;              // turn off comparators
 	Delay_ms(20);            // system wide delay of 20 ms
 	
  ADCON1 = 0x0e;          // Configure Vref and AN0
  TRISA  = 0x01;          // PORTA is output except RA0 (AN0)
  TRISB  = 0x00;          // all PORTB pins are output
  TRISC  = 0x00;          // PORTC is outputs
  
  LCD4_INIT();            // initialize the LCD
  LCD4_OUT("Weight (kg) : ");       // output some text

  while(1)
  {
     temp_res = Adc_Read(0);          // sample a/d converter
     
     temp_res_text = (char *) malloc(5);        // allocate 5 character bytes
     
     // How would i use sprintf function to convert temp_res data into string format
     // in resultant pointer temp_res_text?
     
     LCD4_CMD(142);                   // move cursor position to character #15
     LCD4_OUT(temp_res);              // output the a/d result
     
     free(temp_res_text);             // free allocated character bytes
  }
}

Please let me know if there are any functions that you don't understand as those functions have been tested to work up to the specification so far, hence why I didn't include them b/c they are not the source of the problem.